MBA/PGDM

You have not specified the college you are seeking admission to. But I see that you have a Diploma. Unfortunately, Diploma is not considered as a graduation course. The minimum requirement for applying to MBA is, the candidate must have completed his/her Bachelor's degree with 50% of marks from a recognised university.

If you have experience in the range of 0-1 years, then please do not go for MBA correspondence, go for a regular MBA programme. A person with a good amount of experience in his career or field of interest might find MBA through correspondence helpful. But all fresher's and those who have not settled with a career, you should try to go for regular MBA programs.

That's a reasonably good score, with that score your son can quite easily secure admission in Christ University. Provided he qualifies any other requirements laid out by the University.

Hi,
Please go through this article for how to prepare for an MBA exam:
https://www.shiksha.com/mba/articles/cat-preparation-blogId-20079

MBA is available in Dr. DY. Vidyapeeth Institute of Distance Learning but MBA in project management is not available.

Almost, all the universities around the world (UK, Australia, Canada, etc.) accept GMAT and IELTS test score for MBA course. IELTS can be exempted, but not GMAT.

Your GMAT score is fine, means (Good > 630 > Average). Your college, class 10th and 12th score is also fine. Now, depending on your non-academic profile and job experience, I would suggest you to apply for some other good college as well. IMT (it is not specifically mentioned) doesn't accept GMAT but they do accept CAT and MAT. Anyway, IMT is good and so your profile, but apply for other good universities as well.

You don't need to appear for GRE unless you are planning for MS in the US. What matters the most is GMAT. However, as far I know there is no exemption as such in US universities for GMAT which Means you must need to score good marks in GMAT (it actually differs for every university). Additionally, you also need to have a good band score in IELTS or TOEFL (if the medium of instruction in your last attended university is not English).
Hope this helps.
Good luck.

I don't think it will affect your selection but than it completely depends on the university what criteria they pursue.

To get the admission in christ university you should at least get 50% -60% in your boards exam and you also have to clear their entrance exam and PI.